Refractory brick

ABSTRACT

A refractory brick adapted for use in furnace roof construction and having bonding faces and nonbonding faces and a casing sheet of oxidizable metal carried on at least one of the bonding faces, the casing including a sheet characterized by at least one spacing rib projecting from at least one surface, the rib or ribs being disposed longitudinally along the longest dimension of the bonding faces of the brick and along a line or lines to one side of the centerline and at least one-half the distance from the centerline to one edge of the bonding faces. Preferably, the spacing ribs are disposed in surface engagement with the brick side face and function to space the one surface of the sheet therefrom. The relative size, configuration and positioning of the spacing ribs of the sheet permits substantially complete oxidation of the steel during use without resulting in growth in overall sheet thickness, and maintains uniform bearing stress conditions in furnace roof brick joints.

United States Patent [72] Inventor GrantM.Farrington.Jr.

Marlton,N.J.

211 AppLNo. 789,896

[22] Filed Jan.8,l969

[45] Patented Au|.l0,197l

[73] Assignee General Refractories Company Philadelphia, Pa.

[54] REFRACTORY BRICK FOREIGN PATENTS 3/1956 Austria PrimaryExaminer-Henry C. Sutherland Au0rney-Fidelman, Wolffe & LeitnerABSTRACT: A refractory brick adapted for use in furnace roofconstruction and having bonding faces and nonbonding faces and a casingsheet of oxidizable metal carried on at least one of the bonding faces,the casing including a sheet characterized by at least one spacing ribprojecting from at least one surface, the rib or ribs being disposedlongitudinally along the longest dimension of the bonding faces of thebrick and along a line or lines to one side of the centerline and atleast one-half the distance from the centeriine to one edge of thebonding faces. Preferably, the spacing ribs are disposed in surfaceengagement with the brick side face and function to space the onesurface of the sheet therefrom. The relative size, configuration andpositioning of the spacing ribs of the sheet permits substantiallycomplete oxidation of the steel during use without resulting in growthin overall sheet thickness, and maintains uniform bearing stressconditions in furnace roof brick joints.

Patented Aug. 10, 1971 2 Sheets-Sheet 1 INVENTOR GRANT M. FARRINGTON,JR.

ATTORNEYS Patented Aug. 10, 1971 2 Sheets-Sheet 2 Ja j? ATTORNEYSREFRACTORY BRICK Recently there has been developed high-fired basicbrick having high hot strength which is particularly adapted for useinfurnace roof and arch construction. However, while highfired basicbrick has been proven to give betterroof service than conventionalchemically bonded basic brick, difficulties have been encountered in usedue to expansion problems developed because of oxidation of the steelcasing conventionally provided on furnace brick. Unlike chemicallybonded basic brick, little of the oxidized casing is found to beabsorbed by high-fired basic brick and there is less of a tendency for ahigh-fired basic brick to crush or undergo plastic deformation adjacentthe hot surface of the roof and thus relieve ings have been found toresult in roof failure unless compensation is provided therefor.

Various solutions have been proposed to relieve or minimize expansionstress resulting from oxidation of brick casings. In this respect it hasbeen proposed to include a compressible asbestos sheet in the jointsbetween bricks for the purpose of compensating for both expansion ofbrick casings due to oxidation and thermal expansion of the bricks.However, the provision of asbestos sheets complicates brickinstallation,'increases construction costs, interferes with desiredbonding of casing to brick, and has been found to result in a higheroxidation rate of the casing. Also, it has been proposed 'to reduce thedegree of expansion in a furnace roof by decreasing casing thickness andby increasing the dimensions of the bricks. However, these proposalsfail to completely solve the oxidation problem or bring overall roofexpansion I within desired limits.

Also, it has been proposed to compensate for thermal expansion of theindividual bricks forming a furnace roof by providing brick casings orspacers with dimples, embossments or corrugations which permit thecasing to collapse under high stress conditions. For instance, in U.S.Reissue Pat No. 25.,755, there is disclosed a spacer, wherein one of apair of facing plates is provided adjacent the lower or hot end portionof the brick with a pair of embossments which project from the surfaceof such plate into engagement with a plate carried on an adjacent brick.While this construction compensates in part for thermal expansion of thebricks, it does not compensate for expansion due to oxidation of thespacer plates themselves. Further, when employing this type ofstructure, difficulty has been encountered in achieving proper alignmentof the embossments across any given transverse element or ring of theroof, thereby resulting in improper alignment of the forces which areset up due to thermal expansion of bricks and oxidation growth of thespacer plates. Misalignment of forces 3 has been found to cause snakingor curvature ofthe individualbricks along the roof element or ring whichmay result in complete failure of the roof. Simple spacers or pairs ofdimples in thin steel sheet casings do not possess adequate strength toresist the load between brick in large sprung arches and have been knownto collapse in constructed arches and,

bricks are forced to slide into place. In this type of structure thebearing stress which individual joints will sustain will varysubstantially depending upon the alignment or the relative misalignmentof the casing plate crests, and there exists a tendency for. the platecorrugation to collapse when forces present in the roof structure duringuse tend to force an adjacent brick or bricks to move in a directiontransversely of the corrugations.

Further, it has been proposed to employ casings formed from metals whichare less subject to oxidation than conventionally employed low-carbonsteel. However, use of such metal both increases the cost ofconstruction and may require modification of presently available casingapplying equipment.

in accordance with the present invention there is provided a novelfurnace brick casing design, which permits the utilization ofconventional steel-casing material with high-fired basic brick, whileavoiding the disadvantages of the prior art. The casing is preferablyformed by stamping a flat sheet, usually from a coil, of oxidizablemetal, such as conventionally employed cold-rolled low-carbon steel, toprovide at least one rib on the casing sheet. The extent to which thesheet is deformed, i.e. the height of the projections, depends on thetype of metal employed and is preferably at least equal to the growth inthickness of the nonembossed sheet due to oxidation expected to beencountered during use. The projecting ribs, which serve to space thenonribbed portions of the casing sheet from a casing carried on anadjoining brick when installed in a roof structure, define cavities orvoids adapted to receive the 0xidized layer formed on the casing sheetwhile permitting gradual deformation of the projections upon oxidationthereof. The thus formed casing, even though completely oxidized duringuse, has been found to undergo little or no increase in overallthickness.

Also, the casing is additionally employed to compensate for thermalexpansion of the bricks by increasing the height of the projections overthat required to compensate for oxidation growth. ln this case thebearing strength of such projection may be accurately controlled topermit collapse thereof during use.

in the present invention the casing is formed, preferably from a singlemetal sheet, having a plurality of ribs arranged to provide a particularconformation when formed into a casing around a brick. The sheet isadapted to be wound around the bonding faces of the brick to form acasing structure of generally rectangular cross section, wherein theribs project outwardly from the faces of the brick. The ribs aredisposed on the sheet in a pattern such that when the sheet is conformedto the bonding faces of the brick, there are one or more ribs, on

' oneor more bonding faces, positioned along a line or lines therefore,do not satisfactorily provide expansion relief for plate oxidation orthermal expansion during service.

Further, in Austrian Pat. No. 238,621, there is disclosed a brick casingwherein an oxidizable metal sheet is provided with corrugationsextending either longitudinally or transversely of a brick so as to forma yieldable joint between adjacent bricks. The projecting crests of thecorrugations tend to promote interlocking between mating casing surfaceswhen running along the longest dimension of the brick and at not lessthan half the distance from the center line to one edge of the face.Alternatively, the casing may be applied to the brick by gluing. Thiscan be accomplished by using the casing as single, double or moresections, as desired.

When two or more ribs are provided for each face it is necessary thateach rib be positioned along a line which is at least one half thedistance from the centerline to one edge of the face. The rib canactually be at the outside edge but such a location creates difficultiesof manufacture. Also, the rib can occupy the total space involved,beginning at one half the distance from the centerline to the edge, andextending all the way to the edge. If, however, such a large area ofribwere contemplated, then more than one rib of narrower width could beemployed, so long as each was located farther than one half the distancefrom the centerline to only one edge of the face, and thus, all ribs oneach face one to the same side of the centerline. While any number ofribs may be employed, it is important to note that any or all located onone face of the brick are disposed to only one side of the centerline,and it is intended that the expression at least one half the distancefrom the centerline to one edge of said face be read to indicate thatthe ribs are positioned so that any or all on a given face are disposedto only one side of the centerline and at a certain minimum distancetherefrom.

The dimensions of the ribs are not critical. It is, however,advantageous if the same percentage of brick expansion can beaccommodated in all directions. This may be readily accomplished byproviding the thickness of the ribs in proportion to the thickness ofthe brick. In other words, the extension of the rib above the plane of agiven face will be in direct proportion to the thickness of the brickfrom the face on which the rib is located to the opposite face. But inno event will the extension be less than that required to accommodatethe oxidation growth of the casing plate in use. Ordinarily, the ribswill project outwardly from the face of the brick by an amount at leastequal to the thickness of the casing.

One function of the ribs in addition to the provision of expansion inthe refractory structure, appears in the construction of open hearthroofs, where the shape ofthe bricks is such that one end is slightlysmaller than the opposite end. Such bricks are known as keys. Unless thebrick is very carefully marked to designate one end from the other, itis very easy for the workmen on the job to reverse the keys so that thelarge end of the brick is toward the inner circumference of the arch,which, if not noticed before the furnace is put into service, can resultin premature failure. The provision of the ribs in the present inventionprovides an automatic identification since if the brick is reversed theribs will fall on top of other ribs of adjacent bricks rather thanfalling on the flat ,plate surface as they should. The provision of thealignment of the ribs along the longest dimension of the brick issignificant in that the arrangement facilitates driving of keys duringconstruction. If this were not so, i.e. if horizontal ribs wereprovided, one horizontal rib would be forece to ride over a horizontalrib on an adjacent brick during construction.

The ribs may be formed with tapered side wall surfaces to permitcontrolled collapse or deformation of the projections due to the growthof an oxide layer thereon and to make the individual projections moreresistant to deformation or collapse should forces present in a roofstructure cause adjacent bricks to slide with respect to one another.Alternatively, the ribs may be formed with relatively straight side wallsurfaces in order to increase the bearing strength of relatively highgage casing sheet material.

Alternative casing embodiments are also anticipated, wherein ribs on twoor even three side faces of the brick may be omitted, and wherein theprojection and recess design and arrangement on the casing sheet permitsthe projections to space nonembossed portions of the sheet from a casingsheet of either like or flat surface configuration carried on a joiningbrick ofa roof structure.

The nature of the present invention will be more fully understood byreference to the following description, taken with the accompanyingdrawings, wherein:

FIG. 1 is a perspective view of the preferred embodiment of the presentinvention, a refractory brick having an oxidizable metal casing thereon;

FIG. 2 is a perspective view ofa second configuration showing certainoptional variations;

FIG. 3 is a detail view ofa method ofjoining the edges of the metalcasing;

FIG. 4 is a detail view ofa method for securing the casing in place onthe brick;

FIG. 5 is a schematic view of the arrangement of the brick of FIG. 2incorporated into a monolithic refractory structure;

FIG. 6 is a schematic view of an alternative configuration of the ribswherein two ribs are provided on each bonding face of the brick;

FIG. 7 is a schematic view of still another configuration of the ribs;

FIGS. 8 and 9 show yet other configurations, again in a schematic view;

FIGS. 10, ll, 12 and 13 show in sequence the method of providing thebrick ofthe present invention.

Referring now to FIG. 1, there is shown a refractory brick according tothe present invention comprising brick l and metal casing 2. Metalcasing 2 is carried on the four bonding faces of the brick. Therespective faces of the brick may be rectilinear, trapezoidal or anyother shape known in the manufacture of refractory brick. Disposedlongitudinally along the longest dimension of each face of the metalcasing, are ribs 3. In the embodiment of FIG. 1, there is one rib perbonding face, although as will be seen there may be two or even moreribs per face. The ribs are disposed longitudinally along the longestdimension of the bonding faces of the brick, along a line which is atleast one half the distance from the centerline of the face 2, to theedge of the face of the brick. That is, the distance A from thecenterline 5 to the rib 3 must be at least one half of distance B fromthe centerline to the edge of the face. The ribs 3 project from thesurface of the brick l in such a manner that there remain voids 4between the inner surface of the rib 3 and the face of the brick I. Inthe embodiment of FIG. 1, the ribs 3 are shown having tapered sidewalls,which serve to make the projections more resistant to deformation orcollapse in service.

In FIG. 2, there is shown a refractory brick of the present inventionwith details of the construction techniques utilized. The brick of FIG.2 is the same as that of FIG. I, with the exception that the ribs aredifferently disposed on the casing, and therefore, have a differentdisposition on the faces of the brick. The reference numerals of FIG. 2indicate the same features as those of FIG. 1. In addition, FIG. 2 showsat reference numeral 6 the overlapping joint, resulting from theformation of the casing by the preferred technique ofwrapping" a sheetmetal casing about the brick with a small overlap 6 and spot welding.Permanent positioning of the casing 2 on the body of brick 1 is effectedin FIG. 2 by the provision of the recess and case key projection 11. Theoverlapping joint and the key lock are further shown in detail in FIGS.3 and 4. While other techniques of manufacture are contemplated withinthe scope of the present invention the techniques embodied in FIG. 2 arepreferred for convenience.

In FIG. 3 the overlapping joint of the brick of FIG. 2 is shown indetail. Brick l is provided on one of its faces with recessed groove 9,adapted to receive flange 7, which is formed in the sheet metal of thecasing 2. The thickness of the recess 9 is preferably the same as onethickness of the sheet metal of the casing. The joints formed betweenflange 7 and the opposite end of the sheet, shown at 8, are fastenedpreferably by spot welding. This describes a preferred method ofapplying the casing.

In FIG. 4 the positioning key 11 is shown in further detail. The brick lis provided, on one of its faces, with recess 10. The sheet casing isprovided with key projection 11, which may be impressed in the casingafter it has been formed on the brick, or it may be preformed in aunified step with the provision of ribs 3 and flange 7. The keyprojection 11 engages with the recess in the brick 10 to prevent thecasing from sliding relative to the brick, and thus providing apermanent positioning of the casing on the brick body.

FIG. 5 illustrates the arrangement of the brick of the present inventionin a finished bonded monolithic structure, where bonding faces 2 areshown to be spaced apart by the action of ribs 3. FIG. 5 is shown inschematic form.

In FIG. 6, the schematic view of another embodiment of the presentinvention is shown. In this embodiment two ribs are provided on eachbonding face, and on the narrower bonding face the outermost rib isprovided at the edge of the face. Each of the ribs on each of the facesis disposed at least one half the distance from the centerline to theedge of the face. The embodiment of FIG. 6 illustrates quite clearlythat where a plurality of ribs are provided on a given face, all theribs on that face must be disposed to only one side of the centerline.

In FIG. 7, still another embodiment of the present invention is shown,having still another disposition of the ribs on the face of the brick.In the embodiment of FIG. 7 the narrower faces of the brick have onlyone rib while the wider bonding faces have two ribs each.

. The provision of a plurality of ribs on a given face as shown in FIGS.6 and 7, might be highly desirable where the structural loads to beplaced on the brick, i.e. on the ribs, would exceed the bearing capacityof the particular gage of metal utilized, were only one rib provided. Byproviding a plurality of ribs the bearing capacity is substantiallyincreased.

In FIG. 8, an embodiment of the present invention is shown, in schematicform, having one rib on each bonding face, disposed at the very edge ofthe face.

In FIG. 9, an embodiment is shown having ribs provided on only two ofthe bonding faces.

FIGS. 10, ll, l2, l3 and 14 illustrate the sequence of steps involved inthe preferred method of manufacture of the brick of the presentinvention.

In FIG; 10 there is shown a sheet 'or web of conventional readilyoxidizable, metal casing material, such as mild coldrolled steel. Thelength of sheet material is sufficient to permit it to be wrappedcompletely around the brick at its side faces and with furtheradditional amounts to accommodate the material required for the ribs andfor the marginal overlapping flange area. The sheet is then formed, asshown in FIG. 11, to provide the ribs and overlapping flange. The ribsare shown as recesses 3 and the overlapping flange is shown as 7. Thetechnique whereby the sheet is formed into the appropriate shape is notsignificant to the present invention, however, it is preferred toutilize stamping techniques which are well known in the art, and whichappear to provide the greatest economy and ease of processing.Projection 11 which is adapted to fit into a keyed recess in the brickmay be provided as a part of the original stamping process, although itis also contemplated that the sheet may be formed around a brick andprojection 11 may be subsequently impressed in the sheet to engage withthe recess in the brick.

In FIG. 12 there is shown a brick adapted to receive the casing of thepresent invention, having recessed channel 9, and depression 10, adaptedto receive the key projection 11 of the sheet. While the casing of thepresent invention possess particular utility when used with brick bodiesof the high-strength type, known as high-fired basic brick, having acontent of at least about 50 percent magnesium oxide and varying amountsof other oxides, including oxides of chromium, silica, iron, andaluminum, it will be clearly understood that it may be employed withimproved results in combination with the more conventional chemicallybonded basic bricks. The sheet of FIG. 11 and the brick of FIG. 12 areengaged and the sheet is folded about the brick as shown in FIG. 13.Marginal flange 7 is engaged in recess 9 as shown. Then, as shown inFIG. 14, the flange 7 and the opposed end of the sheet are engaged inoverlapping joint 8 and spot welded.

By providing a wrap around casing structure, wherein a casing sheet isdisposed on each bonding face of the brick body, there can be created amonolithic roof structure wherein all of the individual bricks arephysically locked with respect to all adjacent bricks due to bonding ofadjacent brick casings under high temperature furnace operatingconditions. This permits subsequent repair of bricks within individualfurnace roof rings, without danger that the remaining bricks formingsuch a ring will fall into the furnace.

In each of the foregoing embodiments of the present invention, theprojection of the rib spacing portions with respect to the casing sheetsurface 2 is-at least that necessary to accommodate oxide layer growthsand, preferably, and additional amount to accommodate thermal expansionof the individual bricks. It will be apparent that when modifying theheights of the spacing portions, particular care must be taken inchoosing the gage of the sheet metal employed in forming the casing andthe dimensions in relative placement of the casing ribs so as to insurecontrolled uniform collapse of the side walls of the spacing portions toaccommodate brick growth due to thermal effects.

Casing design requirements, i.e. the number, size and spacing of theribs, vary depending upon such factors as brick composition anddimension, and operating conditions encountered in any given furnaceroof construction. The casings are generally formed from 22 to 26 gage,preferably from 25 to 26 gage, cold-rolled low-carbon steel sheet whichis stamped to provide the spacing ribs. The projection of the ribs abovethe surface of the steel sheet will generally range between about 0.020and 0.060 inches, preferably about 0.030 to 0.045 inches, depending uponthe degree of brick expansion clue to thermal effects for which it isdesired to compensate.

While it has been shown and described preferred embodiment of theinvention, and certain other embodiments thereof, still othermodifications will readily occur to those skilled in the art. Forexample, the utilization of particular refractory materials in theforming of the brick, or the accommodation of unusual shapes thereof,could require certain adaptations of the present invention. It istherefore intended that the invention be limited only by the appendedclaims.

I claim:

l. A refractory brick for use in furnace construction, said brick havingfour bonding faces and two nonbonding faces, and a unitary casing of asingle thickness of oxidizable metal sheet secured on each of saidbonding faces, said casing being of substantially uninterrupted planarsurfaces except for at least one rib and no more than two ribs disposedlongitudinally and extending fully along the longest dimension of atleast two opposing bonding faces, each rib on each bonding face beingalong a line at least one half the distance from the centerline of eachbonding face to one edge of each bonding face, each rib on each bondingface further being located on opposite sides of a plane passing throughthe centerlines of said opposing bonding faces, said ribs on saidopposing bonding faces being adapted to cooperate with ribs of a likecasing secured on bonding faces of an adjacent brick installed in afurnace construction thereby providing for proper orientation andspacing of adjacent bricks during furnace construction wherebysufficient space between adjacent bricks is produced to allow forexpansion of each refractory brick casing.

2. The refractory brick structure of claim 1 wherein both pairs ofopposing bonding faces have at least one rib disposed longitudinallyalong the longest dimension of said bonding faces.

3. The refractory brick of claim 2 wherein each pair of opposing bondingfaces are different widths with the wider of said bonding faces beingprovided with two of said ribs and the narrower of said faces beingprovided with one of said ribs.

4. The refractory brick of claim 2 wherein there are two of said ribs oneach bonding face.

1. A refractory brick for use in furnaCe construction, said brick havingfour bonding faces and two nonbonding faces, and a unitary casing of asingle thickness of oxidizable metal sheet secured on each of saidbonding faces, said casing being of substantially uninterrupted planarsurfaces except for at least one rib and no more than two ribs disposedlongitudinally and extending fully along the longest dimension of atleast two opposing bonding faces, each rib on each bonding face beingalong a line at least one half the distance from the centerline of eachbonding face to one edge of each bonding face, each rib on each bondingface further being located on opposite sides of a plane passing throughthe centerlines of said opposing bonding faces, said ribs on saidopposing bonding faces being adapted to cooperate with ribs of a likecasing secured on bonding faces of an adjacent brick installed in afurnace construction thereby providing for proper orientation andspacing of adjacent bricks during furnace construction wherebysufficient space between adjacent bricks is produced to allow forexpansion of each refractory brick casing.
 2. The refractory brickstructure of claim 1 wherein both pairs of opposing bonding faces haveat least one rib disposed longitudinally along the longest dimension ofsaid bonding faces.
 3. The refractory brick of claim 2 wherein each pairof opposing bonding faces are different widths with the wider of saidbonding faces being provided with two of said ribs and the narrower ofsaid faces being provided with one of said ribs.
 4. The refractory brickof claim 2 wherein there are two of said ribs on each bonding face.